Comprehensive and Detailed Explanation:
The correct answer is C - Data Extract Activity.
* Specifically, a Tracking Extract (a type of Data Extract) can pull all Not Sent events within the past 24 hours.
* After extracting, the data can be moved to SFTP via a File Transfer Activity.
#Why others are wrong:
* A: Report Definition Activity runs standard reports - it doesn't create extract files for automation.
* B: SendLog Extract extracts SendLog DEs, not Not Sent tracking events.
* D: SQL Query Activity manipulates DE data but doesn't extract system event data directly.
Exact Extract from Salesforce Official Documentation:
Salesforce Help - Data Extract Activity Overview:
"Data Extract Activities allow you to retrieve tracking event data such as Sends, Deliveries, Bounces, Not Sent, Opens, Clicks, etc. Use a Tracking Extract type to pull these events into a file for export." (Source:https://help.salesforce.com/s/articleView?id=sf.mc_as_data_extract_activity.htm)
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